## Heat Transfer Performance of Double Tube Hairpin Heat

## Exchager by Using Cfd Analysis with Mgo Nano Fluidat

## Different Volume Fractions

### Dr. P. Srinivasulu , Mr.B.Nagaraju , Sayyad Shabana

1_{ Professor And Hod, }2_{assistant Professor, } 3_{m.Tech (Thermal Engineering) Student }

Dept. Of Mechanical Engineering, "Vaagdevi College Of Engineering" Bollikunta, Warangal, Telangana 506005.

**Abstract: **

Heat exchanger is a device used to transfer heat between one or more fluids. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. In this thesis, MgO nano fluid is mixed with base fluid water is analyzed for their performance in the hair pin heat exchanger. The nano fluid MgO is mixed with water at different volume fractions (0.000625, 0.00125, 0.0025, 0.005 and 0.01). Theoretical calculations are done determine the properties for nano fluids and those properties are used as inputs for analysis.

3D model of the hair pin heat exchanger is done in CREO parametric software. CFD analysis is done on the hair pin heat exchanger with MgO nano fluid at different volume fractions and thermal analysis is done in ANSYS for two materials Aluminum7085 and Copper.

**Keywords:** Finite element analysis, Hair pin heat
exchanger, CFD analysis, thermal analysis.

**I. INTRODUCTION **

Heat exchangers are one of the mostly used equipment in the process industries. Heat Exchangers are used to transfer heat between two process streams. One can realize their usage that any process which involve cooling, heating, condensation, boiling or evaporation will require a heat exchanger for these purpose. Process fluids, usually are heated or cooled before the process or undergo a phase change. Different heat exchangers are named according to their application. For example, heat exchangers being used to condense is known as condensers, similarly heat exchanger for boiling purposes are called boilers. Performance and efficiency of heat exchangers are measured through the amount of heat transfer using least area of heat transfer and pressure drop. A better presentation of its efficiency is done by calculating over all heat transfer coefficient.

Pressure drop and area required for a certain amount of heat transfer, provides an insight about the capital cost and power requirements (Running cost) of a heat exchanger. Usually, there is lots of literature and theories to design a heat exchanger according to the requirements.

**II.LITERATURE REVIEW **

**DESIGN AND ANAYSIS OF DOUBLE PIPE HEAT **

**EXCHANGER ** **USING ** **COMPUTATIONAL **

**METHOD **

**III. INTRODUCTION TO CAD **

Computer-aided design (CAD) is the use of computer systems (or workstations) to aid in the creation, modification, analysis, or optimization of a design. CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing. CAD output is often in the form of electronic files for print, machining, or other manufacturing operations. The term CADD (for Computer Aided Design and Drafting) is also used.

**INTRODUCTION TO CREO **

CREO, formerly known as Pro/ENGINEER, is 3D modeling software used in mechanical engineering, design, manufacturing, and in CAD drafting service firms. It was one of the first 3D CAD modeling applications that used a rule-based parametric system. Using parameters, dimensions and features to capture the behavior of the product, it can optimize the development product as well as the design itself.

**Dimensions of designed double tube Hair-pin heat **
**exchanger: **

**Outer pipe specification Inner tube specification **

Copper tube of U bends I.D. of shell= 19.05 mm I.D. of tube = 8.4 mm Copper tube of U bends I.D. of shell= 19.05 mm I.D. of tube = 8.4 mm

O.D. of shell = 22 mm O.D. of tube = 9.5 mm Center to center distance is taken

Wall thickness= 0.55 mm 127

1.5 - 1.8 times of outer dia. of shell. Thermal conductivity of wall= 385 w/m2K Length of each G.I. pipe =

22.86cm

Effective length of copper tube through which heat transfer could take place= 45cm

Total length of the copper tube = straight part (51cm) + U-shaped bend part (9cm) =60cm

**3D model of hair pin heat exchanger **

**IV. INTRODUCTION TO FINITE ELEMENT **
**METHOD **

FEM/FEA helps in evaluating complicated structures in a system during the planning stage. The strength and design of the model can be improved with the help of computers and FEA which justifies the cost of the analysis. FEA has prominently increased the design of the structures that were built many years ago.

**INTRODUCTION TO CFD **

Computational fluid dynamics, usually abbreviated as CFD, is a branch of fluid mechanics that uses numerical methods and algorithms to solve and analyze problems that involve fluid flows.

**CALCULATIONS TO DETERMINE PROPERTIES **
**OF NANO FLUID BY CHANGING VOLUME **
**FRACTIONS **

**NANO FLUID CALCULATIONS **
**NOMENCLATURE **

ρnf = Density of nano fluid (kg/m3)

ρs = Density of solid material (kg/m3)

ρw = Density of fluid material (water) (kg/m3)

ϕ = Volume fraction

Cpw = Specific heat of fluid material (water) (j/kg-k)

Cps = Specific heat of solid material (j/kg-k)

µw = Viscosity of fluid (water) (kg/m-s)

µ = Viscosity of Nano fluid

Kw = Thermal conductivity of fluid material (water) (W/m-k)

Ks = Thermal conductivity of solid material (W/m-k)

**DENSITY OF NANO FLUID **

ρnf = ϕ×ρs + [(1-ϕ) × ρw]

**SPECIFIC HEAT OF NANO FLUID **

Cp nf = ϕ×ρs×_{ϕ}Cps_{×}_{ρs}+ _{+(}1_{1}−_{−}ϕ_{ϕ} (_{)×}ρw_{ρw}×Cpw)

**VISCOSITY OF NANO FLUID **

**µnf =µw (1+2.5ϕ) **

**THERMAL CONDUCTIVITY OF NANO FLUID **

Knf = _{Ks}Ks+_{+}2Kw_{2Kw}+_{−}2_{2}Ks_{Ks}_{−}−Kw_{Kw}_{ } _{1}1_{+}+_{β}β³_{³}×_{×}ϕ_{ϕ} × kw

**CFD ANALYSIS OF HAIR PIN HEAT **
**EXCHANGER**

**MAGNESIUM OXIDE NANO FLUID **

**VOLUME FRACTION - 0.01 **

**STATIC PRESSURE**

**HEAT TRANSFER CO-EFFICIENT**

**MASS FLOW RATE**

**HEAT TRANSFER RATE**

**THERMAL ANALYSIS OF HAIR PIN HEAT **
**EXCHANGER**

**MATERIAL-COPPER**

**IMPORTED MODEL **

**MESHED MODEL **

**BOUNDARY CONDITIONS**

**TEMPERATURE **

**HEAT FLUX **

**THERMAL ANALYSIS OF HAIR PIN HEAT **
**EXCHANGER **

**TEMPERATURE **

**HEAT FLUX **

V.**RESULT TABLES **

**CFD RESULT TABLES **

**THERMAL ANALSIS RESULTS TABLES **

**CFD ANALYSIS GRAPHS**

**PRESSURE PLOT **

**VELOCITY PLOT **

**HEAT TRANSFER COEFFICIENT PLOT **

**HEAT TRANSFER RATE PLOT **

**THERMAL ANALYSIS GRAPHS **

**VI. **
**CONCLUSION**

In this thesis, MgO nano fluid is mixed with base fluid water are analyzed for their performance in the hair pin heat exchanger. The nano fluid is magnesium Oxide for FIVE volume fractions 0.000625, 0.00125, 0.0025, 0.005 & 0.01. Theoretical calculations are done determine the properties for nano fluids and those properties are used as inputs for analysis. Hairpin Exchangers are available in single tube (Double Pipe) or multiple tubes within a hairpin shell (Multitude), bare tubes, finned tubes, U-tubes, straight tubes (with rod-thru capability), fixed tube sheets and removable bundle.

By observing the CFD analysis results the heat transfer rate value more at magnesium oxide volume fraction 0.01.

By observing the thermal analysis results the heat flux value more for copper material compare with aluminum alloy7085.

So it can be concluded the magnesium oxide nano fluid at volume fraction 0.01 fluid is the better fluid for hair pin heat exchanger and material is copper.

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